In order to research the melting and solidification characteristics of aluminum silicon alloy with elec- tron beam scanning, the valence electronic structure of phases on alloy have been calculated based on the ＂ Empirical Electronic Theory in solid and molecule＂ （EET）. The microstructure and mechanical properties are respectively measured by means of the optical microscopy, scanning electron microscope and microhardness tester. The effects of the dimensions of silicon on the hardness of alloy are analyzed. The reason which is the cause of a crack on the center of silicon is discussed. The experimental results show that it is more difficult for Silicon and eutectic structure to destroy than that of aluminum. After the electron beam surface scanning, sam- ples are divided into melting zone, transition zone and matrix zone, and Silicon is obviously refined. The mor- phology size of the silicon：in melting 7,one is less than 8.5 μm,its highest hardness is 1.39 times of that in substrate. The cause of crack in center of silicon is the density difference around silicon after dissolving.%为研究电子束扫描铝硅合金表面的熔化及凝固特征,基于价电子理论计算了合金内各相的价电子结构;利用金相显微镜、扫描电镜、显微硬度计等测试了试样微观组织与机械性能;分析了凝固后硅相形貌尺寸对材料硬度的影响;探讨了硅相中心产生裂纹的原因.研究表明：硅相及共晶体的结构破坏要比铝的结构破坏难;电子束表面熔凝处理后,试样分为熔化区、过渡区和基体三个区域;且经电子束扫描处理后,硅相得到了明显细化;熔化区内硅相的形貌尺寸小于8.5μm,该区的最高硬度是基体硬度的1.39倍;溶解后硅相周围的密度差是硅相中心产生裂纹的原因.
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